Control apparatus for molding presses

Abstract

A control apparatus provides for automatic programmed sequencing of pressure bumps at precisely determined pressures in a molding press and optionally provides for full pressure or low pressure cure at the conclusion of the bumping operation. The control apparatus comprises a press pressure monitor that measures press clamp pressure and produces an output signal indicative of the measured press pressure, and a control circuit that compares the output signal with a program selected one of a number of reference signals respectively indicative of bump pressures at which a bump may be desired and directs the press to perform a bump upon a predetermined relationship between the output signal and reference signal, such being indicative of the attainment of the bump pressure indicated by the then selected reference signal. Upon completion of the bumping operation, either full or low pressure cure may be effected. For full pressure cure, the control circuit permits press clamp pressure to increase to full pressure which is then maintained during cure. For low pressure cure, the control circuit compares the output voltage of the press pressure monitor to a program selected reference signal indicative of the desired cure pressure and upon a predetermined relationship therebetween indicative of the attainment of such cure pressure, directs the press to maintain such pressure within a prescribed range.

What is claimed is: 
     
       1. A method of controlling the bumping operation of a press comprising the steps of: (a) supplying an output signal proportional to press pressure,   (b) selectively and sequentially supplying reference signals respectively indicative of different pressures at which bumps may be performed in accordance with a predetermined program,   (c) comparing the output signal with each selectively supplied reference signal,   (d) supplying a control signal upon a predetermined relationship between the output signal and then selected reference signal, and   (e) directing the press to perform a bump in response to such control signal.   
     
     
       2. A method of controlling the bumping operation of a press, comprising the steps of: (a) sensing press pressure and providing an output signal indicative of sensed press pressure,   (b) sequentially producing a number of preselected reference signals respectively indicative of bump pressures,   (c) sequentially comparing the output signal with the reference signals, and   (d) producing a control output signal in response to a predetermined relationship between each reference signal and the output signal, and wherein step (b) includes providing program command signals respectively indicative of the reference signal to be compared at each sequential bump and selecting and supplying the reference signals for sequential comparison with the output signal in accordance with the command signals, and   comprising the further steps of providing a further program command signal indicative of one of the reference signals corresponding to a desired cure pressure, supplying such command signal to a reference signal selector after the last bump has been performed for selecting such one of the reference signals for comparison with the output signal, and then directing the press to hold press pressure in response to a predetermined relationship between the output signal and such one of the reference signals.     
     
     
       3. A method of controlling the bumping operation of a press, comprising the steps of: (a) sensing press pressure and providing an output signal indicative of sensed press pressure,   (b) sequentially producing a number of preselected reference signals respectively indicative of bump pressures,   (c) sequentially comparing the output signal with the reference signals, and   (d) producing a control output signal in response to a predetermined relationship between each reference signal and the output signal, and wherein step (b) includes producing a number of reference signals respectively indicative of different bump pressures and selectively determining which reference signal is to be compared with the output signal for each sequential bump.     
     
     
       4. The method of claim 3 comprising the further step of controlling the duration of each bump with a bump duration timer. 
     
     
       5. The method of claim 4 comprising the further step of starting the bump duration timer upon the press pressure dropping to a nominal pressure common to each bump. 
     
     
       6. A method of controlling the bumping operation of a press, comprising the steps of: (a) sensing press pressure and providing an output signal indicative of sensed press pressure,   (b) sequentially producing a number of preselected reference signals respectively indicative of bump pressures,   (c) sequentially comparing the output signal with the reference signals,   (d) producing a control output signal in response to a predetermined relationship between each reference signal and the output signal, and   (e) directing the press to perform a bump in response to the control output signal.   
     
     
       7. The method of claim 6 wherein step (a) includes producing an analog output signal proportional to sensed pressure. 
     
     
       8. The method of claim 6 wherein step (a) includes using a pressure transducer to produce an analog output signal proportional to sensed pressure. 
     
     
       9. The method of claim 8 wherein step (b) includes sequentially producing preselected analog reference signals, and step (c) includes comparing the analog output signal and reference signals with an analog comparator. 
     
     
       10. The method of claim 6 wherein step (b) includes providing program command signals respectively indicative of the reference signal to be compared at each sequential bump and selecting and supplying the reference signals for sequential comparison with the output signal in accordance with the command signals. 
     
     
       11. The method of claim 10 comprising the further step of reading a program memory device and providing the command signals in accordance with program information carried by the program memory device. 
     
     
       12. The method of claim 11 comprising the further step of utilizing a program memory device of non-volatile type having the program information fixedly encoded therein. 
     
     
       13. An apparatus for controlling the bumping operation of a molding press, comprising means for supplying an output signal indicative of press pressure, and control means for comparing the output signal with program selected reference signals respectively indicative of different bump pressures and, in response to a predetermined relationship between the output signal and then selected reference signal, directing the press to perform a bump, and cure pressure control means for controlling the pressure of the press during cure, said control means including means for producing a number of reference signals respectively indicative of different bump pressures,   means for selectively determining which reference signal is to be supplied for each sequential bump,   means for comparing the output signal with the then supplied reference signal and supplying a control signal in response to a predetermined relationship therebetween, such being indicative of the attainment of the bump pressure indicated by the then selected reference signal, and   means responsive to said control signal for directing the press to perform a bump,   said means for selectively determining including programmable means for providing command signals respectively indicative of the reference signals to be supplied to said means for comparing for sequential bumps and means for selecting and supplying a reference signal to said means for comparing in accordance with a command signal provided by said programmable means,   said programmable means producing a command signal indicative of one of the reference signals corresponding to a desired cure pressure,   said means for selectively determining further including means for supplying said command signal to said means for selecting and supplying after the last prescribed bump has been performed whereupon such one of the reference signals is supplied to said means for comparing,   said cure pressure control means including means responsive to the control signal produced by said means for comparing upon a predetermined relationship between the output signal and such one of said reference signals for directing the press to hold press pressure,   said means for selectively determining further including bump step counter means for counting the number of bumps that have been performed and providing a signal representative of such number to said programmable means so that when said counter means moves to the next sequential step, said programmable means will provide to said means for selecting and supplying the command signal dictating the reference signal for the next sequential step,   said programmable means producing a signal representative of the total number of bumps to be performed during a molding cycle, and   said control means further including bump step comparator means for comparing the signal representative of such number of bumps that have been performed with said signal representative of the total number of bumps to be performed and, upon a match therebetween, directing the means for selectively determining to supply the command signal indicative of such one of the reference signals corresponding to a desired cure pressure to said means for selecting and supplying.   
     
     
       14. In a press having cooperating mold sections defining a mold cavity therebetween and control apparatus for controlling the bumping of mold clamping pressure, the improvement comprising said control apparatus including: a pressure transducer for providing an analog output signal directly proportional to mold pressure sensed by said transducer,   means for automatically sequentially producing plural preselected analog reference signals,   analog comparator means for sequentially comparing the analog output signal of said transducer with said plural analog reference signals, and   means for generating a control output signal in response to a predetermined relationship between each of said reference signals and the output signal of said transducer.   
     
     
       15. The apparatus of claim 14 wherein said control means further includes means responsive to the control output signal from said means for generating for directing the press to perform a bump. 
     
     
       16. In a press having cooperating mold sections defining a mold cavity therebetween and control apparatus to control the bump operation of the press, the improvement comprising said control apparatus including: transducer means for measuring press pressure and providing an output signal indicative of the measured pressure,   means for sequentially supplying reference signals respectively indicative of bump pressures,   means for sequentially comparing the output signal with the reference signals and supplying a control signal upon a predetermined relationship between each of the reference signals and the output signal which is indicative of the press attaining the pressure indicated by the then supplied reference signal, and   means for receiving the control signal from said means for sequentially comparing and for directing the press to perform a bump in response thereto,   said means for receiving and directing including timer means for controlling the duration time of the bump, and means for starting the bump duration timer upon the press pressure dropping to a nominal pressure common to each bump.   
     
     
       17. The apparatus of claim 16 wherein said means for starting the bump duration timer includes means for supplying a nominal reference signal indicative of such nominal pressure to said means for comparing in response to said control signal, said means for comparing then comparing the output signal of the transducer means with said nominal reference signal and upon a predetermined relationship therebetween supplying a start signal to said timer means. 
     
     
       18. The apparatus of claim 17 wherein said means for supplying includes means for selecting a selected one of a number of different reference signals respectively indicative of different press pressures and means for supplying said means for selecting a command signal dictating such selection. 
     
     
       19. The apparatus of claim 18 wherein said means for supplying a nominal reference signal supplies the same nominal reference signal for each bump. 
     
     
       20. In a press having cooperating mold sections defining a mold cavity therebetween and control apparatus for controlling the bumping of mold clamping pressure, the improvement comprising said control apparatus including: a pressure transducer for providing an analog output signal directly proportional to mold pressure sensed by said transducer,   means for automatically sequentially producing plural preselected analog reference signals,   analog comparator means for sequentially comparing the analog output signal of said transducer with said plural analog reference signals,   means for generating a control output signal in response to a predetermined relationship between each of said reference signals and the output signal of said transducer, and   means responsive to the control output signal from said means for generating for directing the press to perform a bump,   said means for automatically sequentially producing including means for producing a number of analog reference signals respectively indicative of different bump pressures and means for selectively determining which analog reference signal is to be supplied to said analog comparator means for each sequential bump.   
     
     
       21. The apparatus of claim 20 wherein said analog comparator means has a reference signal input, said means for selectively determining includes a decoder having an output connected to said reference signal input and a number of inputs selectively connectable to said output, and said means for producing includes reference signal generators connected respectively to the inputs of said decoder. 
     
     
       22. The apparatus of claim 21 wherein said reference signal generators each include variable attenuating means connecting a common signal source to the respective input of the decoder. 
     
     
       23. The apparatus of claim 22 wherein said variable attenuating means includes a potentiometer. 
     
     
       24. The apparatus of claim 21 including bump duration timer means for controlling the duration of the bump. 
     
     
       25. The apparatus of claim 24 wherein said bump duration timer means includes mans for adjusting the duration time of the bump. 
     
     
       26. The apparatus of claim 11 wherein said decoder has an inhibit input for receiving the control output signal from said analog comparator means and inhibiting the output of said decoder in response thereto, and further comprising means for impressing a nominal reference signal on the reference signal input of said analog comparator means when the output of the decoder is thusly inhibited. 
     
     
       27. The apparatus of claim 26 wherein said analog comparator means produces a second control signal in response to a predetermined relationship between the output signal of the transducer and the nominal reference signal, and said second control signal starts said bump duration timer means. 
     
     
       28. The apparatus of claim 11 including means for starting the bump duration timer upon the press pressure dropping to a nominal pressure common to each bump step. 
     
     
       29. The apparatus of claim 28 wherein said means for starting the bump duration timer includes means for supplying a nominal reference signal indicative of such nominal pressure to said analog comparator means in response to said control signal, said analog comparator means then comparing the output signal of the transducer with said nominal reference signal and upon a predetermined relationship therebetween supplying a start signal to said timer means. 
     
     
       30. The apparatus of claim 20 wherein said means for selectively determining includes programmable mans for providing command signals respectively indicative of the reference signals to be supplied to said analog comparator means for sequential bumps and means for selecting and supplying a reference signal to said analog comparator means in accordance with a command signal provided by said programmable means. 
     
     
       31. The apparatus of claim 30 wherein said analog comparator means has a reference signal input and said means for selecting and supplying includes decoder means having an output connected to said reference signal input and a number of inputs selectively connectable to said output in accordance with the command signals, and said means for producing includes reference signal generators connected respectively to the inputs of said decoder means. 
     
     
       32. The apparatus of claim 30 wherein said means for selectively determining further includes bump step counter means for counting the number of bumps that have been performed and providing a signal representative of such number to said programmable means so that when said counter means moves to the next sequential step, said programmable means will provide to said means for selecting and supplying the command signal dictating the reference signal for the next sequential bump. 
     
     
       33. The apparatus of claim 30 including cure pressure control means for controlling the pressure of the press during cure. 
     
     
       34. The apparatus of claim 33 wherein said programmable means produces a command signal indicative of one of the reference signals corresponding to a desired cure pressure, said means for selectively determining further includes means for supplying said command signal to said means for selecting and supplying after the last prescribed bump has been performed whereupon such one of the reference signals is supplied to said analog comparator means, and said cure pressure control means includes means responsive to the control signal produced by said analog comparator means upon a predetermined relationship between the output signal and such one of said reference signals for directing the press to hold press pressure. 
     
     
       35. The apparatus of claim 30 wherein said programmable means includes means for reading a program memory device and providing the command signals in accordance with the program information carried by said program memory device. 
     
     
       36. The apparatus of claim 35 wherein said program memory device is of the non-volatile type having program information fixedly encoded therein. 
     
     
       37. The apparatus of claim 36 wherein said program memory device is a printed circuit card. 
     
     
       38. The apparatus of claim 16, wherein said program memory device includes a printed circuit card and said reader means includes decoder means for deciphering the printed circuit card. 
     
     
       39. The apparatus of claim 38 including step counter means for providing a count signal to said reader means representative of the number of bumps that have been performed so that when said counter means advances upon performance of a bump, said reader means will provide to said means for selecting and supplying the command signal dictating the reference signal to be selected and compared with the output signal of said transducer for the next sequential bump. 
     
     
       40. The apparatus of claim 39 wherein said programmable means produces a count signal representative of the total number of bumps to be performed and further including bump step comparison means for comparing the signal from said step counter means with said count signal and upon a predetermined relationship therebetween, supplying a signal to said means for directing to inhibit inhibiting the performance of any further bumps. 
     
     
       41. The apparatus of claim 40 including cure pressure control means for receiving the signal from said bump step comparison means and in response thereto, controlling the pressure of the press during cure. 
     
     
       42. The apparatus of claim 41 wherein said programmable means produces a command signal dictating the selection of a cure pressure reference signal indicative of cure pressure and supplies it to the means for selecting and supplying in response to the signal from said bump step comparator means whereupon the reference sigal indicative of cure pressure is supplied to the analog comparator means, and said cure pressure control means includes means responsive to the control signal produced by said comparison means upon a predetermined relationship between the output signal of the transducer and the reference signal indicative of cure pressure for directing the press to hold pressure.